Just did an 8.8 swap in my 85SS with adjustable uppers. You can adjust the rear upper control arms and it will pull/push the rear end from side to side. I measured from the inside of the rim to the frame rail to get it basically the same both sides. Then set the pinion angle. This video helped explain things.
Something could have been changed being it was modified. My 70 Cutlass is 3/4" to the right. I thought it looked uneven. Putting on 275/60R15 proved my theory. No damage, just the axle is to the right, body related. When I replace the rear quarters, it will get fixed. Inspect and measure.
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